Hydraulic-pneumatic impact device



Dec. 10, 1968 A- A. BUEHLER ET AL HYDRAULIC-PNEUMATIC IMPACT DEVICE Filed Nov. 23, 1966 3 Sheets-Sheet l INVENTORS ALO/S' A. BUEHLER EWALD H. KURT Dec. 10, 1968 A. BUEHLER ET AL 3,415,328

HYDRAULIC-PNEUMATIC IMPACT DEVICE 3 Sheets-Sheet 2 WWW A. H. mm. L A5 WQQ 3 Sheets-Sheet 3 Fm bbx m R 5. J i E A i 1 Jill; M W A E Dec. 10, 1968 A A. BUEHLER ET AL HYDRAULIC-PNEUMATIC IMPACT DEVICE Filed Nov. 25, 1966 United States Patent 3,415,328 HY DRAULIC-PNEUMATIC IMPACT DEVICE Alois A. Buehler, Easton, Pa., and Ewald H. Kurt, Phillipsburg, N..I., assignors to Ingersoll-Rand Company, New York, N.Y., a corporation of New Jersey Filed Nov. 23, 1966, Ser. No. 596,525 16 Claims. (Cl. 173-105) ABSTRACT OF THE DISCLOSURE This disclosure relates to rock drills of the cam actuated type and includes a hydraulic motor for reciprocating the hammer. A chamber in the drill casing is supplied with compressed air to provide a pre-loaded air spring which provides the energy for delivering an impact to the drill steel. A hydraulic motor rotates the hammer and a cam and follower raise the hammer into the chamher to further pressurize the air. On further rotation, the hammer is released and the compressed air forces the hammer toward the drill steel to deliver an impact. An air cushion is provided to prevent the hammer from striking the casing end wall. The impacting force may be varied by increasing or decreasing the air chamber pre-load and speed of rotation of the hammer.

This invention relates to a rock drill of the impact type and in particular, but not exclusively, to a cam actuated rock drill. In some prior rock drills of this type, the hammer is provided with a cam. A pair of rollers are rotated relative to the cam and hammer so that the hammer is raised against a helical spring. The compressed spring supplies the impacting force to the hammer. It has been found that the drill hammer, as it is raised against the compression spring, will tend to break the compression spring after a relatively few number of cycles. In rock drills of this type, there has been no means for limiting movement of the hammer in the direction toward the drill steel. As the hammer moves toward the drill steel to deliver an impact, the entire force of the hammer after it moves beyond a certain point must be absorbed by the casing end wall. This will tend to fracture both the casing and hammer. In present cam actuated drills it is diflicult to use a clean out fluid such as air or liquid to blow the cuttings out of the drill hole. This is because the cam and rollers are located internally of the hammer. This prevents the blow pipe from being placed through the piston. Present rock drills of this type are not designed so that the clean out air may be admitted to the top of the drill steel. The only place clean out air could be admitted without interfering with the drills operation is at some point between the top of the drill steel and the drill steel chuck.

It is, therefore, the principal object of this invention to provide a novel drill of the hydraulic cam actuated type.

It is another object of this invention to provide a rock drill of this type which is capable of delivering a greater impact and is more durable.

It is another object of this invention to provide a rock drill in which the impact delivered to the drill steel can be varied easily.

In general, the aforementioned and other objects are carried out by providing a casing, a drill steel extending into the casing and a hammer mounted for reciprocal movement within the casing. Integrated cam means and follower means are disposed within the casing for raising and quickly releasing the hammer when one of said cam and follower means is rotated. Means are provided for rotating one of the cam means and follower means. Means are provided for maintaining one end of the casice ing under fluid pressure for forcing the hammer towards the drill steel when the hammer is released and means for varying the speed of reciprocation of the hammer.

The foregoing and other objects will become apparent from the following description and drawings wherein! FIG. 1 is a general overall View of the rock drill and operating equipment of this invention:

FIG. 2 is a schematic diagram of the actuating equipment;

FIG. 3 is a longitudinal view of a first portion of the rock drill of this invention and joined to a second portion of the drill along line X-X of FIG. 3A;

FIG. 3A is a longitudinal sectional view of the second portion of the rock drill shown in FIG. 3 and joined to the first portion along line X-X of FIG. 3A;

FIG. 4 is a section taken on line 4-4 of FIG. 3 in the direction of the arrows;

FIG. 5 is a fragmentary detail of a. portion of FIG. 3 with the hammer delivering an impact to the drill steel;

FIG. 6 is a detail of the hammer on a reduced scale;

FIG. 7 is a schematic of the cam profile; and

FIG. 8 is a fragmentary detail of a modification of this invention on a reduced scale.

Referring a FIG. 1 there is shown a rock drill generally indicated at 1. The drill shown is of the drifter type although it is not intended that this invention be limited to any particular type of drill. The drill includes a drill steel 2, a hammer mechanism 3, a supporting leg 4, and a drill guide 5. The operating mechanism includes a compressor 6 and first and second pumps 7 and 8 driven by an engine 9. If desired, these may be mounted on a platform 10 for ease of transportation.

Referring now to FIGS. 3 and 3A, the hammer 'mechanism includes a casing having a first or cylinder portion and a second or forward portion 21. The drill steel 2 extends into the forward position 21 of the casing and is provided with a flange 22 which is held in a chuck 23. An end piece 24 for holding the drill steel in place is threaded into the casing portion 21. There is provided means for rotating the drill steel 2 relative to both the casing and the hammer 40. This rotating means includes a motor 25 which may be either pneumatic or hydraulic or, if desired, electric. The motor drives a shaft 26 mounted in bearings 27 and 28 and is provided with a spur gear 29 which engages a spur gear 30 mounted on a shaft 31. The shaft 31 is mounted for rotation in bearings 32 and 33. The shaft 31 carries a smaller diameter gear 34 which engages gear teeth 35 on the chuck 23. As the motor 25 is driven, the chuck 23 is then rotated thus rotating the drill steel 2 through the series of gears 29, 30, 34 and 35. The gear ratio may be whatever is desired but a ratio of about 8 to 1 has been found to be satisfactory. The means for rotating the drill steel is per se known and, by itself, is not intended to be a limitation of this invention. However, the use of means for rotating the drill steel relative to the hammer in this type of rock drill produce advantages not found in prior drills of this type.

A hammer or piston is mounted within the cyiinder 20 for rotative and axial movement relative to the cylinder 20. The hammer 40 has a passage 41 therethrough and is provided with a tubular member 42 which is coaxial and extends into a passage 36 in the drill steel. The tubular conduit is used to supply fluid for cleaning cuttings from the drilled hole. The blow tube or pipe 42 is connected to a supply of air or other fluid under pressure through a hose 43. This hose is connected to a passage 44 in the drill and a fitting 45 which is sealed at 46. Fluid under pressure goes through the hose 43, passage 44 and into the blow tube 42. The air under pressure then goes through the passage 36 in the drill steel 2 and is used to blow cuttings out of the drilled hole.

The hammer 40 includes an elongated portion 47 which is adapted to strike the drill steel 2 and a cam 50. The cam 50 is integral with the outer periphery of the hammer. As best shown in FIGS. 6 and 7, a cam profile includes a pair of gradual rises 53 and a pair of sharp drops 54 at the end of the rise followed by a pair of flat portions 55. A pair of rollers or follower means 56, FIG. 5, extend into the cylinder through the casing portion 20. These rollers include a generally cylindrical member 57 mounted in bearings 58 and secured to the housing by any suitable means such as a plate 59 and bolts (not shown).

As the piston is rotated, the rollers 56 engage the cam 50 for the major portion of a revolution. When the rollers reach a rise, the piston is moved outwardly. As the hammer continues to rotate, the roller will reach the sharp drop. The rollers will become disengaged from the cam surface and the hammer will be released and tend to move downwardly quickly to deliver an impact to the drill steel. In order to force the piston down with sufficient force to deliver a useful impact to the drill steel, some means must be provided to give force to the downward movement. We have chosen to use fluid under pressure rather than a compression spring as we have found air pressure to be more reliable. Air under pressure is supplied from the compressor 6 through a conduit 90 to a passage 91 in the rock drill into an annular groove 92. The air passes through a plurality of holes 93 into the upper portion or chamber 94 of the cylinder 20. If desired, there may be a drilled out portion or recess 98 with an adjustable block 99 for varying the size of the chamber 94. Although only one drilled out portion 98 is shown, there may be a plurality of such portions depending on the needs of the particular drill. A conduit 95 is provided in the cylinder wall 20 to selectively connect the chamber 94 through a passage 96 into the lower side 97 of the cylinder. A drain port 100 is provided in the cylinder wall connecting the lower cylinder portion 97 with atmosphere. This port is used to allow oil which may accumulate in the chamber 97 to drain to atmosphere and thus prevent dieseling" which may result when an oil-air mixture is subjected to high pressure and the heat of friction. Primarily, this port allows the chamber 97 to be exhausted with each upward stroke of the hammer.

Means for rotating the hammer are provided and include a hydraulic motor 70 of any suitable type. This motor rotates a spur gear 71 which is mounted on a splined motor shaft 74 in bearings 72 and 73. The spur gear 71 meshes with a spur gear 75 mounted in bearings 76 and 77. The spur gear 75 has a shaft 78 mounted thereon having splines 79. The hammer 40 has a sleeve member or insert 80 having internal splines. The insert 80 is secured to the hammer by suitable threads. The splines 79 on the shaft 78 fit with the internal splines on the insert 80. The hammer 40 will thus rotate with the shaft 78 and reciprocate thereon.

OPERATION The compressor 6 supplies air at a constant pressure through conduit 90 to the chamber 94 on the upper side of the piston 40. An engine driven fixed delivery pump 7 supplies hydraulic fluid to the motor 70 to rotate the hamrner 40. As the hammer rotates the cam 50 and rollers 56 raise the hammer into the chamber 94-. As the hammer is raised or retracted, it compresses the air in the chamber 94 to a great extent and when the rollers 56 reaches the sudden drop 54, the hammer is quickly released and the compressed air in the chamber 94 forces the hammer 40 down towards the drill steel 2 to deliver an impact to the drill steel.

Although in some applications it may be desirable to have the flow path between the compressor 6 and the chamber 94 blocked as soon as the hammer begins to move upward and thus begin to compress the air in chamber 94 immediately, we prefer to postpone the compression of fluid in chamber 97 until the hammer 40 nears the top portion 49. In the preferred embodiment, chamber 97 and compressor 96 remain in communication as the hammer is raised until the annular rib 61 sealingly fits into the drilled out portion 48. This closes the passage from chamber 94, through ports 93, groove 94, passage 91 and the hose to the compressor 6. The air trapped in the chamber 94 is then compressed as the hammer 40 is raised further to provide energy to force the hammer towards the drill steel and deliver an impact when the hammer is quickly released.

In order to prevent the hammer from striking the casing which will tend to fracture the casing as well as the hammer in the event the drill steel 2 drops below the normal impact point, an air cushion is provided in the lower portion 97 of the cylinder 21). When the hammer travels below its normal impact point, the passage 96 is opened allowing air under pressure to enter the conduit charging the lower cylinder portion 97. As the hammer continues to move downward, the port 101 is closed and the air in the chamber 97 is compressed thus providing a fluid cushion to prevent the hammer from contacting the end 60 of the cylinder wall.

As the hammer is rotated and moves upward, the passage 96 is closed thus shutting off the flow of compressed air to chamber 97. As the hammer continues to move upward, the passage 106 is opened allowing any oil in the portion 97 to drain.

The hammer 40 is rotated by a hydraulic motor 70 through gearing 71 and 75 and the splined shaft 78. The motor is driven by a pump 7 which has fixed displacement. This pump is driven by an engine 9. The pump 7 receives fluid such as oil from a reservoir 110 through line 111 and pumps it through a directional valve 112. If the valve 112 is in the on position, the fluid is pumped to the motor 70 through line 114. The oil is then exhausted from the motor through line 115 and a restriction 116, through the valve 112, and line 113 to the reservoir. If the valve 112 is in the off position, the fluid is pumped through the valve 112, line 113 and back to the reservoir 110.

The chamber 94 is pressurized by a compressor 6 through a shut-off valve 120, an air pressure regulator 121, and line 90. When a light impact is to be delivered to the drill steel, the chamber 94 is pressurized a minimum amount such as 50 p.s.i. Thus, when the hammer 40 is raised by the cam 50 riding on rollers 56, the pressure in the chamber 94 is raised. When the rollers come to the sudden drop 54 on the cam 50, the force pressurizing the air in the chamber 94 is released. The pressure then forces the hammer forward to deliver an impact to the drill steel 2. If a greater impact force is required, the chamber 94 is initially pressurized to a greater extent by opening the regulator 121 a greater amount. Because the initial pressure in the chamber 94 is increased, when the hammer is in the raised position, the pressure is increased. Therefore, the hammer moves forward faster when the rollers 56 become disengaged from the cam and delivers a greater impact to the drill steel 2.

Since the speed at which the hammer will move forward will vary with the pressure in chamber 94, the speed of rotation of the hammer must be coordinated to the pressure in the chamber 94 in order to insure proper operation of the drill. If the cam strikes the rollers 56 at the wrong point, the cam or rollers will tend to break. This can best be illustrated by what would happen if the hammer were rotated at a speed too great for the speed of axial movement of the hammer. If the hammer moved toward the drill steel too slowly as compared to the rotational speed of the hammer, when the cam contacted the roller after the sharp drop, the roller and cam would engage each other on the rise 53. This would tend to result in breakage of the cam. To prevent this breakage, the cam and rollers must engage each other at some point on the fiat portion 55 such as between the points A and B. This may be done by coordinating the speed of the motor 70 to the air pressure in the chamber 94.

In order to maintain the speed of rotation of the hammer in harmony with its speed of axial movement, a variable delivery hydraulic pump 8 is provided. This pump may be driven by the same engine 9 as the first pump 7. When the pressure in chamber 94 increases above a predetermined value such as the maximum pressure which the pump 7 will be effective, a valve 122 in line 123 is opened. Pressure responsive valve 122 is such that as the pressure in chamber 94 increases, it operates to increase the delivery of the pump 8 thus allowing the speed of motor 70 to be varied. When the valve 122 is opened, pump 8 receives fluid from the reservoir 110, through line 111 and pumps it through line .124, one way valve 125, to the directional valve 112 and to motor 70. A restriction 126 is provided in line 123 to eliminate rapid fluctuations in pressure which result when the hammer is moving upward. This prevents the delivery of pump 8 from fluctuating as the pressure in chamber 94 varies rapidly.

The pump 8 is of the variable displacement type. By using this type of pump, the motor speed may be set at any point between a minimum which is the speed attained by the fixed displacement pump 7, and a maximum which is the speed of the motor when the fixed displacement pump is operating at capacity combined with the variable displacement pump.

A safety valve 127 is provided to insure that the motor 70 does not receive greater fluid than it can use and the system does not break down.

In cam actuated impact tools, it has been found that breakage of rollers and cams often occurs because the cam and rollers engage each other on the rise after the sudden drop. One of the reasons for this breakage is the failure to coordinate the speed of rotation with the speed of axial movement of the hammer. Another reason is pointed out by the application of D. K. Skoog filed concurrently with this application on Nov. 23, 1966 and having Serial No. 596,608. This application points out that when the roller reaches the sudden drop in the cam, the motor will tend to race or speed up suddenly for a brief period of time. This sudden racing of the motor results in the hammer rotating faster. The roller will then strike the cam 50 on the rise 53. As is fully described in the aforementioned application of D. K. Skoog, some means may be provided to limit rotation of the hydraulic motor and thus the hammer for a brief period of time to eliminate the racing of the motor.

Even though the motor speed is limited for a brief period of time, the hammer 40 will tend to rotate due to inertia. This tendency of the hammer to rotate must be absorbed by the splines on the insert 80 coacting with the splines 79 on the shaft 78. The force due to inertia on these splines will tend to fracture the splines. In order to compensate for this the embodiment of FIG. 8 may be used. In this embodiment the shaft 78 is provided with spiral splines 79A. The spiral is preferably about 12 but may be other values depending on the particular drill. If spiral splines 79A are used, they will absorb the rotation of the hammer and eliminate breakage by allowing the hammer to rotate to a slight extent. This rotation is not enough to allow the cam and rollers to engage each other on the rise 53.

From the foregoing it can be seen that the objects of this invention have been carried out. By using the cam on the outside as opposed to the inside of the piston, a greater cam length can be used. This allows a more gradual increase in the rise to prevent breakage of both the cam and rollers. The rollers can be placed in the casing from the outside which allows the rollers to be replaced without disassembling the entire drill. The cam on the outside of the hammeralso allows the use of a blow tube for chip cleaning purposes.

By using an air spring rather than a standard helical spring, the hammer may be run on an air cushion. This eliminates the danger of both breakage of the spring and the casing or hammer.

It is intended that the foregoing be merely that of a preferred embodiment and that the invention be limited only by that which is within the scope of the appended claims.

We claim:

1. An impact tool comprising:

a casing:

a hammer mounted for reciprocal movement within said casing and adapted to deliver an impact to a workpiece;

integrated cam means and follower means disposed within said casing for retracting and quickly releasing said hammer when one of said means is rotated;

means for rotating one of said cam means and follower means;

said hammer and one end of said casing defining a chamber on one side of said hammer;

means for supplying to said chamber fluid under a predetermined pressure for moving said hammer towards a workpiece when it is released to thereby deliver an impact to the workpiece; and

means for supplying fluid under pressure to the other end of said casing for preventing said hammer from contacting the other end of said casing.

2. The rock drill of claim 1 wherein said hammer has a coaxial bore therethrough for conducting fluid under pressure.

3. The rock drill of claim 1 wherein said means for supplying fluid under pressure to the other end of said casing is conduit means for intermittently conducting fluid under pressure from said chamber.

4. The rock drill of claim 1 wherein said rotating means includes a hydraulic motor.

5. The rock drill of claim 1 wherein said cam means is on the outer periphery of said hammer and said follower means is a roller mounted on said casing.

6. The rock drill of claim 5 wherein said cam means is rotated and said rotating means is a motor for rotating said cam means and hammer.

7. The rock drill of claim 6 wherein said motor means is connected to said hammer by splines.

8. The rock drill of claim 7 wherein said splines are helical.

9. In combination with a rock drill having a casing, a drill steel extending into said casing, and a hammer mounted within said casing for delivering an impact to said drill steel, a system for reciprocating said hammer comprising:

integrated cam means and folower means disposed within said casing for raising and quickly releasing said hammer when one of said cammeans and 01- lower means is rotated;

means for rotating one of said cam means and follower means;

means for supplying compressed air to said casing on one side of said hammer for moving said hammer towards said drill steel when said hammer is released to deliver an impact to said drill steel;

means varying the impacting force of said hammer; and

means for varying the speed of rotation of one of said cam means and follower means.

10. The system of claim 9 wherein said cam means is carried by said hammer, said follower means is a roller mounted on said casing and said rotating means is a hydraulic motor connected to said hammer and is driven by a first engine driven pump at a minimum speed.

11. The system of claim 10 wherein said first engine driven pump is of the constant delivery type for driving said hydraulic motor at a minimum speed.

12. The system of claim 11 wherein said means for varying the impacting force of said hammer includes means for increasing the air pressure on one side of said hammer.

13. The system of claim 12 wherein said rotational speed increasing means is an engine driven pump of the variable delivery type which in conjunction with said first engine driven pump drives said hydraulic motor at a variable speed above said minimum speed 14. The system of claim 13 wherein said second engine driven pump is responsive to an increase in air pressure on said one side of said hammer.

15. The rock drill of claim 1 further comprising means for sealing said chamber when said hammer has been retracted a predetermined distance so that further retraction of said hammer increases the pressure in said chamber 16. The system of claim 9 wherein said means for varying the impacting force of said hammer includes means for increasing the air pressure on one side of said hammer and said means for varying the speed or rotation of one of said cam means and follower means is coordinated with said means for varying the impacting force of said hammer so that an increase in air pressure results in an increase in the speed of rotation.

References Cited UNITED STATES PATENTS JAMES A. LEPPINK, Primary Examiner.

US. Cl. X.R. 

